Overheated! What to check first. 4.6 V8.

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MrGorsky

MrGorsky

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I am currently on a camping trip.

Before setting off I checked all my fluids, and topped up the water. I have a very small leak from the valley gasket, so it does use a bit of water over time.

I drove 70 miles to the campsite on Motorway and A roads, with roof box on and car loaded to the gunwales, and everything was great.

Whilst out doing a bit of shopping I filled up with fuel, and when I went to start the car it ran really rough, misfiring and all sorts, but when revved it ran smooth again and settled down so I thought nothing of it.

About 20 miles later I overheated, needle went way up, red light came on, I stopped immediately and let it cool. The expansion tank was empty, and the top hose was very hard too.

I slowly undid the cap and as pressure subsided some water filled the expansion tank again from the cooling system. I poured what water I had in the car in the expansion tank, and started up and drove back checking the temp needle every 100 yards.

It's been fine ever since. Starts and runs fine, got me back to the campsite without overheating, but I haven't driven more than 30 miles in it yet.

I've got to drive home at some point so what and where should I be checking? I can check for leaks easily, but what else should I be looking for.

Does the fact it ran so rough, and the hard top hose point to HG failure? And if that's the case why is it running so smooth now?

Any help gratefully received!
 
Sorry to hear that. Might there be somewhere local that can do a quick check for exhaust gasses in the coolant?
 
Rough Running could be because the temp sensor was telling the ECU it was a fecking hot engine and the ECU was trying to fuel the engine just so....a quick rev of the engine circulated cooler coolant that you added through the system and the sensor detected a lower temp and the ECU compensated fuelling to adjust for this different temp.

Check the operation of your viscous fan, was the top hose rock solid or just firm??, you should be able to dent the hose with good thumb pressure, but rock solid could indicate an issue!

Keep it topped up and as Stufer suggests find a local place to do a sniff test, or even get on t'internet and find a supplier locally of those colour change test kits!
 
Top hose was very firm, but I could dent it. Much firmer than I was expecting though!

There will be a Halfords nearby I'd have thought. I'm not in the wilds or anything, so I could get a kit.

Game on!
 
What role does the expansion cap play in all this? They can fail can't they? And do the V8s have plastic impellers that fail?
 
Holts or similar rad and head sealant. I have used these in the past when on long trips and slight water loss. Cured it with no issues but do follow the instructions only takes 10mins or so. Good idea to carry some water and at evey stop check the level say after you have been for a coffe or so. If it works, even for a few months its worth having peace of mind while on a trip.
 
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MrGorsky said:
What role does the expansion cap play in all this? They can fail can't they? And do the V8s have plastic impellers that fail?
Click to expand...
They can fail closed and not relieve pressure in the system causing hard hoses....

Maybe your cap is knackered, but that doesn't explain the loss of coolant, unless your Valley Gasket leak has been the prime cause and when the system was under extra pressure due to failed cap, it really started to squirt out of the leak!
 
MrGorsky said:
What role does the expansion cap play in all this? They can fail can't they? And do the V8s have plastic impellers that fail?
Click to expand...

If the expansion cap fails then the coolant looses pressure (pressure stops the coolant from boiling), even new caps should be tested in a pan of hot water as i'm told. The original waterpumps do have plastic impellers that fail, i fitted a metal type on mine last year.
 
Thanks for all the suggestions chaps,

The rain has stopped (for now) so I've been and checked a few things...

*Viscous fan passed newspaper test. Fan stopped spinning when engine cold, doesn't when engine warm.

*Thermostat is opening, bottom hose gets warm at operating temperature.

*No leaks from rad, hoses, or anywhere else that I can see....unless they open up when things get really hot.

*Engine started first time, and idles smoothly.

*No steam or white smoke from exhaust pipes when engine hot or cold.

*Heater works fine

*No evidence of mayonnaise in oil filler cap. I know this means nothing really, but it all looks normal.

I did have to top up quite a bit of coolant this morning with the engine stone cold, however that might be because I cleared any air that might have been in the system during the run back to camp after the overheat.

I've checked the easy obvious stuff now haven't I?

If it is a failing HG, can they come and go? Seems odd to me that if the HG has failed the symptoms haven't repeated themselves on the way back to camp.

Is there a way to check the operation of the water pump without taking it off? If mine is the original plastic one, it'll be past it's best as I've just passed 91,000 miles.

I'll be carrying lots of water and keeping a watchful eye on the temp gauge for the journey home. Perhaps I should join the AA before setting off.
 
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Always join a breakdown service with a RR - trailered back with them twice in seven years and overdue for the third time! - in your circumstances I would not hesitate - I'm with ADAC the German breakdown service tons cheaper particularly if travelling into EU.
 
hi mrgorsky , hey i just found a long screwdriver that will be on its way to you shortly , moved house few weeks ago n found it so will get if off to u shortly and thanks very much ,,, Now re your overheat dont want to scare you but when mine went last year and cost me a complete top hat rebuild " not cheap " it was found to be caused by two little hoses about 6 or 8 ml they rocker cover had been off and when all put back together the two hose clips werent tightened up ???????? anyway another story !!!!!!! there situated just behind the a/c unit attached to the block in front of the radiator as you stand looking at engine from front i dont know what they do or where they go but i do know if they leak they cost you a fffff fortune !!!!!!!! the worst of it was i never ever noticed them before till it was too late ..anyway worth a check and hope its nothing too serious ,, cheers matey n good luck
 
hi mate , mines a thor engine done by turners of rugby excellent job ,,,includind head re- skim and new waterpump with metal impelar and top hat liners ,, cost £3070.00 plus cost of engine out and refit .. by the way just thinkin thewre that you had problem earlier with rad knackered so if yours wasnt bled properlet i.e. all air out cos its a rite bastard to o then overtime and the fact that its all loadesd up then its caused latest problem so hopefully if you make sure its bled properly now it will solve the problem ...fingers crossed ,,,, i believe the way to do it is start up from col with expansion cap off and just let it idle till it bubbles up in expansion box and keep toppin up to level as airs blow out apparently takes about 20 mins to do properly so no rush ,,this is what i can remember !!! others on here may know better always happy to learn ,, good luvk cheers mozz
 
+1 mozz,

Also, it helps to lift the front up so the expansion tank is highest (i parked mine with the OSF wheel on a big wooden sleeper).
 
MrGorsky said:
No hurry Mozz. How much is a top hat linered block these days? I think if it came to it I'd get one.
Click to expand...
Not much change from £1800 I would have thought...

HGF's can 'come and go' (although don't actually do that...they are still there) but as the engine warms and expands, this can cause the 'leak' in the HG or crack in the block/head to be more evident....

Also not sure how testing a cap in hot water would show anything as they relieve at a pressure not at a temperature!

Also a Cap Failing closed will increase pressure and allow the coolant to boil at a higher temp and as such send the gauge higher, only a cap failing open will reduce pressure and make the coolant boil at a lower temp thus not efficiently allowing the engine to run at a higher temp until such time that the coolant will have been expelled through an open cap and the temp gauge rises due to lack of coolant! I know this cos stupidly I didn't refit the cap on the L322, girlfriend took it to work and 11 miles down the road, temp gauge shot up loads of steam from under the bonnet and expelled 9 litres of coolant. I was not flavour of the month that's for sure!
 
there u go gorsky yuor away camping so should have loads of big logs to lift car up then !!!! where are you ????????? im at caravan at moment in sunny lincolnshire ,, till next tuesday , cheers mozz
 
Saint.V8 said:
Not much change from £1800 I would have thought...

HGF's can 'come and go' (although don't actually do that...they are still there) but as the engine warms and expands, this can cause the 'leak' in the HG or crack in the block/head to be more evident....

Also not sure how testing a cap in hot water would show anything as they relieve at a pressure not at a temperature!

Also a Cap Failing closed will increase pressure and allow the coolant to boil at a higher temp and as such send the gauge higher, only a cap failing open will reduce pressure and make the coolant boil at a lower temp thus not efficiently allowing the engine to run at a higher temp until such time that the coolant will have been expelled through an open cap and the temp gauge rises due to lack of coolant! I know this cos stupidly I didn't refit the cap on the L322, girlfriend took it to work and 11 miles down the road, temp gauge shot up loads of steam from under the bonnet and expelled 9 litres of coolant. I was not flavour of the month that's for sure!
Click to expand...

Sorry, getting my caps & stats mixed up....long weekend :(
 
Not wanting to cause unnecessary worry but when I had occasional symptoms of overheat (needle would suddenly fly straight to red), especially under load (uphill on motorway) it was eventually diagnosed as cracked block; the crack would periodically open up when stressed. :( That was 5 years ago, touch wood, the top hat block was a lucky deal I got out of the warranty. Anyway, last resort to investigate.
 
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